Tandem trailer system

ABSTRACT

An intermediate trailer for use between a standard tractor and a standard trailer, the intermediate trailer having a chassis mounted at its rear end, consisting of a first portion which is fixed to the trailer and a second portion which is slidable relative to the first portion from a first position under the trailer to a second position extending rearwardly of the trailer, the second portion having wheels mounted thereon.

This is a continuation of co-pending application Ser. No. 702,009, filedon Feb. 15, 1985, now U.S. Pat. No. 4,598,924, which is a divisional ofco-pending application Ser. No. 520,993, filed on Aug. 9, 1983, and Ser.No. 294,775, filed on Aug. 20, 1981, now U.S. Pat. No. 4,400,004.

BACKGROUND OF THE INVENTION

In the transportation industry, the use of tandem trailer rigs hasbecome very important, mainly because of its cost-effectiveness. This isbecause such an arrangement uses only one driver and one tractor at atime, while the load carrying capacity is twice as great. The maindifficulty experienced in the past with the using two trailers in tandemis the method by which they are joined together. If, for instance, oneuses a standard bogie, there are two articulations, one of which isunder the rear end of the front trailer and one of which is under thefront end of the rear trailer. Such a double articulation is dangerous,because it permits several kinds of buckling and similar motions betweenthe two trailers, thus leading to accidents. In my U.S. Pat. Nos.3,933,374 and 4,030,171, I suggested that a solution to this dangerousproblem could be brought about by use of an extension protruding beyondthe rear of the front trailer. While this arrangement is generallysatisfactory, it has the drawback that the intermediate trailer isalmost entirely committed to use in tandem rigs and has very little usefor running single. Furthermore, it is difficult to back up to a loadingdock even when it is provided with the hinged platform shown in thepatent. These and other difficulties experienced with the prior artdevices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide atandem trailer system in which the connection between the trailersprovides a single point of pivot or articulation.

Another object of this invention is the provision of a tandem trailersystem in which the connection between the trailers remains permanentlywith one of the trailers and, therefore, is not subject to pilferage orvandalism, as is true when a bogie is left by itself.

It is another object of the instant invention to provide a tandemtrailer system in a special forward trailer, which special trailer canbe used by itself.

It is another object of the instant invention to provide a tandemtrailer system in a special forward trailer, which special trailer canbe used by itself.

A still further object of the invention is the provision of a tandemtrailer system in which the connection between the trailers remainspermanently with the front trailer, which front trailer, nevertheless,can be moved close to a loading dock.

It is a further object of the invention to provide a tandem trailersystem which is simple in construction, which is inexpensive tomanufacture, and which is capable of a long life of useful service witha minimum of maintenance.

With these and other objects in view, as will be apparent to thoseskilled in the art, the invention resides in the combination of partsset forth in the specification and covered by claims appended hereto.

SUMMARY OF THE INVENTION

In general, the invention consists of a trailer unit adapted to be drawnbehind a highway tractor and behind which unit can be drawn a secondstandard trailer. The unit consists of a cargo container and a chassison which the container is mounted. The chassis has a first upper portionand a second lower portion, the second portion being longitudinallyslidable relative to the first portion from a first position generallyco-extensive with the first portion to a second position where itextends beyond the end of the cargo container. A first attaching meansis associated with the front end of the container for connection to thehighway tractor and a second attaching means is associated with thesecond portion of the chassis, so that, when the second portion is insecond position, another trailer can be attached to it. Wheels aremounted on the said second portion of the chassis.

More specifically, a pair of locking pins are mounted on the secondportion for transverse movement to engage apertures in the first portionwhen the second portion is in the first or second position; the pins,therefore, serve to hold the first and second portions against relativesliding movement in the first and second position. The wheels areprovided with pneumatic brakes and the locking pins are provided with apneumatic actuator cylinder. A selector valve is provided to connect asource of pressure air selectively to the brakes or the cylinder, sothat the locking pins are released when the brakes are locked and thepins are engaged when the brakes are free. The lower portion is providedwith three pairs of wheels, the wheels being mounted so that one pair isat the front end of the lower portion, one pair is at the rear end, andone pair is in the middle; the second attaching means is a fifth wheellocated between the middle and rear pair of wheels.

BRIEF DESCRIPTION OF THE DRAWINGS

The character of the invention, however, may be best understood byreference to one of its structural forms, as illustrated by theaccompanying drawings, in which:

FIG. 1 is a side elevational view of a trailer unit embodying theprinciples of the present invention showing two trailers operating intandem,

FIG. 2 is side elevational view of a front trailer at a loading dock,

FIG. 3 is a side elevational view of the trailer unit using only onetrailer,

FIG. 4 is a rear elevational view of the trailer unit taken on the lineIV--IV of FIG. 3,

FIG. 5 is a transverse vertical sectional view of the trailer unit takenon the line V--V of FIG. 3,

FIG. 6 is an enlarged sectional view of a portion of the apparatus,

FIG. 7 is a horizontal sectional view of the apparatus,

FIGS. 8 and 9 are schematic cross-sectional views of the invention,showing locking means in two different conditions,

FIG. 10 is an enlarged transverse sectional view of a portion of theapparatus showing a locking pin in use, and

FIG. 11 is a schematic circuit view of pneumatic apparatus used in thetrailer unit.

FIG. 12 is a side elevational view of a portion of the trailer unit,

FIG. 13 is a transverse vertical sectional view of a portion of thetrailer unit,

FIG. 14 is a side elevational view of a portion of the trailer unit,

FIG. 15 is a plan view of the trailer unit during turning, and

FIG. 16 is a side elevational view of the trailer unit.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIG. 1, which best shows the general features of theinvention, the trailer unit, indicated generally by the referencenumeral 10, is shown as being drawn behind a highway tractor 11. Thetrailer unit in turn, is drawing a second trailer unit 12 behind itself.The trailer unit 10 consists of a cargo container 13, at the rear end ofwhich is carried a chassis 14. The chassis has a first upper portion 15and a second lower portion 16. The second portion 16 is longitudinallyslidable relative to the first portion 15 from a first position in whichit is generally co-extensive with the first portion to a second portionin which it extends beyond the end of the cargo container 13, as shownin FIG. 1. A first attaching means 17 extends downwardly from theforward portion of the container 13 for connection to the fifth wheel ofthe tractor 11. A second attaching means 18 in the form of a fifth wheelis associated with the second portion 16 of the chassis, so that, whenthe second portion is in the second position, another trailer 12 can beattached to it. A set 19 of wheels is mounted on the said second portionof the chassis.

FIG. 2 shows the manner in which the container 13 can be unloaded. Thesecond portion 16 remains in the second position, but a platform isprovided to allow a lift truck or similar unloading apparatus to becarried into the container.

FIG. 3 shows the manner in which the container 13 can be moved over theroad by itself behind the tractor 11. The second portion 16 is in thefirst position, that is to say, is co-extensive with the first portionof the chassis. At that time the attaching means 18 lies under thecontainer and the wheels 19 are entirely beneath the container.

Referring next to FIGS. 4, 5, and 6, which shows the details of thefirst portion 15 and the second portion 16, it can be seen that thefirst portion 15 is provided with two spaced, parallel I-beams 21 and22. The second portion 16 consists of two similar I-beams 23 and 24 heldin spaced, parallel relationship. As shown in FIG. 6, the undersurface25 of the I-beam 21 rests on the upper surface 26 of the I-beam 16,while a similar relationship takes place between the I-beams 22 and 24.Guides 27 are attached to the I-beams 23 and 24 and form part of thesecond portion 16; these guides envelope the bottom inner flanges of theupper I-beams 21 and 22.

As shown in FIGS. 7, 8, and 9, a pair of locking pins 28 and 29 aremounted on the second portion 16 for transverse movement to engageapertures 31 of the first portion 15 when the second portion 16 is inthe first or second position. These pins serve to hold the first andsecond portions against relative sliding movement when in the said firstor second positions.

FIG. 10 shows the details of the locking pin 28 and the manner in whichit engages an aperture 31.

Referring to FIG. 11, it can be seen that the wheels 19 are providedwith pneumatic brakes 32, while the locking pins 28 and 29 are providedwith a pneumatic actuator cylinder 33. A selector valve 34 is providedto connect a source of pressure air selectively to the brakes 32 or thecylinder 33 so that the locking pins are released when the brakes arelocked and the pins are engaged when the brakes are free. The brakes areprovided with the conventional system, including a valve 46, for usewhen running over the road.

FIG. 6 shows the provision of slide pads, formed preferably of Teflon,attached to the upper surface 26 of the I-beams 23 and 24 to facilitatesliding motion between the first and second portions. The guides 27 arealso provided with slide pads 36 to facilitate relative sliding of theI-beams 26 and 22.

As is particularly evident in FIG. 1, the lower portion 16 is providedwith three pairs of wheels 37, 38 and 39, these making up the set 19 ofwheels. The wheels are mounted so that the one pair 37 is located at thefront of the lower portion 16, one pair 39 is at the rear end, and onepair 38 lies between them substantially closer to the set 37. A secondattaching means 18 in the form of a fifth wheel is located between themiddle and rear pair of wheels 38 and 39, respectively.

As is particularly evident in FIG. 2, a platform 41 is provided betweenthe cargo container 13 and the rear end of the chassis 14. The platformcan be moved so that it extends only a short distance beyond the rearend of the container. The platform is hingedly connected to the chassisnear the rear end of the cargo container and normally lies against thecontainer door 42. A cable 43 is connected to the platform to controlits movement. Legs are provided to support the platform against movementeven if considerable weight is placed on it.

FIG. 12 shows the manner in which a leaf spring 47 is mounted on thesecond portion 16 of the chassis. It overlies and supports the axle 48of the wheel set 39 in such a way that the axle underlies the pivotalaxis of the second attaching means 18.

FIG. 13 shows the manner in which the second attaching means 18 islocated within the space defined by the first portion 15 of the chassis.This feature permits it to reside under the container 13 when the secondportion is nested under the container, as shown in FIG. 3.

FIG. 14 shows the manner in which the second portion 16 of the chassisis provided with a leaf spring 49 to support the axle 51 of the frontwheels 37. A leaf spring 52 with a stabilizer 53 is used to support theaxle 54 associated with the intermediate wheels 38.

In FIGS. 15 and 16 are shown the cables 55 carried by the second portion16 to supply electrical current and pressure air to the rear trailer 12.These cables are carried on a rod 56 which is connected to the secondportion 16 through a flexible spring 57. The dimensions of the cables55, rod 56, and spring 57 are selected to permit them to lie between theI-beams 23 and 24 of the second portion 16 when it is in the firstposition under the first portion 15, as indicated in broken lines. FIG.15 shows the manner in which the location of the second attaching means18 is selected to allow the forward corners of the rear trailer 12 toavoid contact during turning with the rear of the front railer 13.

The operation and advantages of the present invention will now bereadily understood in view of the above description. In FIG. 1, whichshows two trailers 12 and 13 in tandem, it can be seen that the onlyconnection between them is at the attaching means 18, which means that asingle pivot joins the trailers and the dangers of articulation abouttwo pivots is not present. There is no bogie that would be left behindwhen the rear trailer is dropped off at its destination or when aportion of the highway is reached in which tandem operation isforbidden. Normally, the unloading of the container 13 would take placein the manner shown in FIG. 2 with the platform 41 in horizontalposition, having been lowered to that position by means of a cable 43. Aplate 44 rests on the fifth wheel 18 and legs 45 are provided to giveadditional support for the platform. This allows a forklift truck toenter the container from the dock.

At the same time when the rear trailer has been dropped off it ispossible to use the trailer 13 and the tractor 11 by themselves. At thattime, the apparatus takes the condition shown in FIG. 3.

In order to move the lower portion 16 from one position to another, itis possible to use the braking system shown in FIG. 11. If the valve 34is operated to move the actuating cylinder 33, the locking pins 28 and29 are in locked position and the brakes 32 are free, so that theapparatus can roll on the wheels 37, 38 and 39 without difficulty. Whenit is necessary to move the lower portion 16 from one position to theother, this is done also by means of the valve 34. If, for instance, theportion 16 is shown in the condition shown in FIG. 1 and it is desiredto move it to the first position shown in FIG. 3, it is only necessaryto move the valve 34 to a second position in which the brakes 32 receivepressure air, thus locking them against rolling. At that time thecylinder 33 is released, thus allowing the springs in the system to pullthe locking pins 28 and 29 out of their position 31. When this is done,the tractor and the container 13 are moved backwardly. Since the wheelsbrakes 32 in the wheels 19 are locked in place this causes the firstportion 15 of the chassis 14 to slide rearwardly over the second portion16. Eventually, a limiting position is reached, as shown in FIG. 3, andthe valve 34 is changed back to the position shown in FIG. 11 where theactuating cylinder 33 causes the locking pin to move into place and lockthem in the first or front condition, the wheels are, therefore, free.Tractor 11 and the container 13 are then free to move over the road as asingle unit. The normal brake system is operative on the brakes 32 atthat time.

As shown in FIGS. 12 and 14, the axles 48, 51 and 54 are mounted abovetheir respective springs by use of shackles. This allows the use ofstandard size wheels, even though the second attaching means 18 islocated at a low enough level to permit the rear trailer 12 to be astandard trailer unit.

FIG. 15 indicates the manner in which the entire unit, including thetractor 11, the front trailer 13, and the rear trailer 12, can turn on avery small radius. More specifically, the front corners of the reartrailer 12 clear the rear end of the front trailer 13 by substantialamounts during turning.

FIG. 16 shows clearly the way in which the cables 55 on their supportrod 56 and spring 57 are pressed downwardly into a storage position whenthe second portion 16 slides from its rear, second position to itsfront, first position. When the reverse movement takes place, the cablesspring upwardly into the functional position for connection to thecoupling element on the front end of the rear trailer 12. An alarm isprovided that is energized when the pins are released and remainsoperative when moving the sliding elements from one position to theother.

It is obvious that minor changes may be made in the form andconstruction of the invention without departing from the material spiritthereof. It is not, however, desired to confine the invention to theexact form herein shown and described, but it is desired to include allsuch as properly come within the scope claimed.

The invention having been thus described, what is claimed as new anddesired to be secured by Letters Patent is:
 1. Trailer system,comprising:(a) a trailer unit, including a cargo container to be drawnbehind a highway tractor and behind which can be drawn a second trailerunit, (b) a chassis on which the container is mounted, the chassishaving an upper portion and a lower portion of substantially equallength, the lower portion being formed of at least two spaced, parallelbeams, the said lower portion being longitudinally slidable relative tothe upper first portion from a first portion generally co-extensive withthe upper portion to a second position where it extends beyond the endof the cargo container, (c) a first attaching means associated with thefront end of the container for connection to the highway tractor, (d) asecond attaching means including a fifth wheel associated with the lowerportion of the chassis, so that, when the second portion is in thesecond position, another trailer can be attached to it, the secondattaching means being located on the lower portion far enough rearwardlythat the front end of the second trailer unit can swing relative to thecargo container during turning without striking the rear end of thecargo container, and (e) three sets of wheels mounted on the said lowerportion of the chassis.
 2. Trailer system to be drawn behind a highwaytractor and behind which can be drawn a second trailer unit,comprising:(a) a cargo container, (b) a chassis on which the containeris mounted, the chassis having a first upper portion and a second lowerportion, the second portion being longitudinally slidable relative tothe first portion from a first position generally co-extensive with thefirst portion to a second position where it extends beyond the end ofthe cargo container, the first upper portion of the chassis consistingof a pair of flanged beams held in spaced, parallel relationship forattachment to the container, the second lower portion of the chassisconsisting of a similar pair of flanged beams connected together inspaced, parallel relationship and underlying the first portion, so thatthe undersurface of the flange of each flanged beam of the first portioncontacts the upper surface of the flange of the corresponding flangedbeam of the second portion, a plurality of guides joining the flangedbeams of the second portion to flanged beams of the first portion, slidepads being provided between the facing surfaces of the flanges of theflanged beams, (c) a first attaching means associated with the front endof the container for connection to the fifth wheel of a highway tractor,and (d) wheels mounted on the said second portion of the chassis, thelower portion being provided with at least two sets of wheels, thewheels being mounted so that one pair is at the front end of the lowerportion and one pair is at the rear end, wherein a fifth wheel islocated above the set of wheels located at the rear end of the lowerportion, so that, when the second portion is in the second position,another trailer can be attached to it, the fifth wheel being located onthe lower portion far enough rearwardly that the front end of the secondtrailer unit can swing relative to the cargo container during turningwithout striking the rear end of the cargo container.
 3. Trailer systemas recited in claim 2, wherein a pair of locking pins are mounted on thesecond portion for transverse movement to engage apertures in the firstportion when the second portion is in the first or second position andhold the first and second portions against relative sliding movementwhen in the first or second position, wherein the wheels are providedwith pneumatic brakes, wherein the locking pins are provided with apneumatic actuator cylinder, and wherein valve means is provided toconnect a source of pressure air selectively to the brakes or thecylinder, so that the locking pins are released when the brakes arelocked and the pins are engaged when the brakes are free.